1. Field of the Invention
The present invention generally relates to measuring devices and, more particularly, to a device for measuring inner diameters of container finishes.
2. Description of the Related Art
In the manufacture of containers, certain dimensions are required to be within predetermined tolerance limits in order for the containers to function properly. In particular, the upper surface of the container, commonly known as the finish, must be maintained within certain manufacturing tolerances in order to provide adequate cap retention for a liquid tight seal to be formed between the container finish and the container cap.
Variations in the dimensions of containers, particularly plastic containers, may occur during molding or trimming operations due to many factors, including differences in the molds used to form the containers, shrinkage of the containers after molding, materials used, curing temperatures, and trimming operations. For containers that will hold fluids, including consumer products such as detergents and bleaches, it is important that the inner diameter of the container finish be within predetermined limits so that a fill tube to fill fluids into the container may enter the container without being obstructed. Variations with the inner diameter of the finish generally arise when the two mold halves are joined together, which results in an indentation. The indentation narrows the entry of the container and may obstruct the entry of the fill tube. Another problem that narrows the container finish is related to the design of the finish. Some detergent or bleach bottles, especially the ones with handles, may have an inner lip or shelf that extend into the finish. The shelf is formed along the mold part line and provides a smooth liquid flow from the bottle. Such lips or shelves located at the bottle neck may again obstruct the entry of the fill tube. In order to determine whether the inner diameter of a container finish is within predetermined dimensional tolerances, generally a sampling of the containers being produced is measured to determine actual dimensions.
Although it may vary depending on the container type, in general such sampling methods include manual measurement with a caliper. During the measurements, the calipers are positioned just off the part line and then the caliper extensions are inserted into the finish. The calipers are opened until contact with the inner walls is made. In order to avoid any false readings resulting from the indentations or the lip, however, the operator must line up the caliper contact surface just away from the center of the finish and try to hold the calipers parallel to the finish. However, such measurements are inconvenient and will include inaccuracies due to the manual placement of the calipers, which vary depending on the expertise of a particular user.
Accordingly, it would be desirable to provide a gauge that measures the true inner dimensions of a container finish.
The gauge system of the present invention provides an effective tool to inspect container finish defects occurring during the manufacture of the containers.
In one aspect of the present invention, a gauge system for measuring internal diameters of tubular openings includes a support shaft; a planar surface coupled to a first end of the support shaft and extending perpendicular to the shaft; a first measuring rod having a tapered end with a plurality of reference markings; and a holder member comprising a first end and an aperture positioned at the first end is adapted to receive the first measuring rod.
Specifically, the planar surface supports a container in an upright position. The container comprises a tubular neck having an opening with a first predetermined inner diameter and a second predetermined inner diameter. The tapered end of the measuring rod is adapted to pass through the opening of the tubular neck. The aperture in the holder allows the rod to move parallel to the vertical axis and from an initial position into an extended position. The holder includes a pivot portion to pivotally mount the holder on a second end of the support shaft so as to allow a user to move the holder member about the support shaft and relative to the planar surface and position the first measuring rod above the opening of the tubular neck of the container. When the measuring rod is urged into the extended position, the measuring rod moves vertically into the tubular neck thereby allowing the user to determine the second diameter of the tubular neck with respect to the reference markings.
In another aspect of the present invention, a process for measuring an inner diameter of a bottle finish includes the steps of providing a container comprising a tubular finish having an upper opening with a first predetermined diameter and an inner diameter wherein the inner diameter is smaller than the first predetermined diameter; placing the container on a planar surface of a measuring device in an upright position; positioning a measuring rod of the measuring device above the opening of the container wherein the measuring rod has a tapered end with a plurality of reference markings, wherein the tapered end of the measuring rod is adapted to pass through the upper opening of the container finish; urging the measuring rod into an extended position and into the upper opening of the tubular neck; and determining the inner diameter of the tubular neck with respect to the reference markings.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.